This might be a technical question in the civil forum.....but which is harder on an aircraft: continuous long haul flights or numerous short hops like this WN
The long haul jetliner might not be doing as many cycles per day but is constantly under the stress of pressurized flight
Continuous shorthaul is far harder on the aircraft. Takeoffs and landings (especially landings) are the main points of flight that stress an airframe. Shorthaul generates more of these.
As for pressurization: for an aircraft, BEING pressurized is not nearly as stressful as the process of BECOMING pressurized. Each time an aircraft is pressurized and depressurized, it adds stress to the airframe. The time spent pressurized at high altitude does stress the airframe a bit but this effect is swamped by the effect of pressurizing and depresurizing.
Here's an illustration. Blow a balloon up and let it sit for an hour. Now take a second balloon and blow it up, deflate it, and then blow it up again continually for an hour. After an hour, which balloon would be in better shape? Aircraft (and all pressurized vessels) are like balloons - it is the change in pressurization that causes the most stress, not the pressurization itself.
For the airframe - it is cycles (takeoffs and landings) that matter, not hours or miles because of the reasons mentioned above. That is why airframe maintenance is scheduled more according to cycles than hours. A plane used for shorthaul will undergo more stress and therefore need more airframe maintenance because it is generating cycles much faster than a longhaul plane.
As for engines, the same thing is true but to a lesser degree. Engine wear is mainly determined by how many hours an engine is run - but the number of times it is brought to takeoff thrust also plays a role. My guess is that the high number of times a shorthaul aircraft's engines have to go to takeoff thrust outweigh the greater number of hours a longhaul engine accumulates - so a shorthaul engine undergoes more stress on most days.
This does NOT mean that shorthaul aircraft are unsafe because they wear out more quickly. They do need more maintenance per hour and day flown than longhaul aircraft do, but this is accounted for in regulations and in airline maintenance practices.
SHORT.... Shorthaul flying is much harder on aircraft, systems and engines than longhaul flying is. This is true just about however you measure it, and it is a major factor in the extra expense of shorthaul flying. The fact that Southwest has a very low cost per seat flown one mile is all the more remarkable because they do a lot of shorthaul flying.